1899.] OSTEOLOGY OF TITR TCTBIXVUES. 407 



b' . Posterior borrlpv of .stermmi with four deep notches ; spina externa 



bkmt or bifid Puffinus. 



Majaquetts. 



Bulweria, 



Frion. 



(Estrelata. 



Pat/odroma. 



c'. Outer pair of notches obliterated or feebly developed (sometimes forming 



fenestrae) Priocella. 



Thalassoeca. 



Fulmanis. 



Priofinus. 



cV. Posterior border of sternum with 4 very slight notches ; corpus sterni 

 vrith pneumatic opening on anterior region of dorsal surface. 



Ossifraga. 



b. Coracoid grooves forming a right angle with the sternum ; base of coracoids 

 not more than ^ the width of the long axis ; sternal ribs almost en- 

 tirely confined to anterior lateral process ; furculum without a distinct 

 hypocleideuiu ; posterior border of corpus sterni entire... Pelccanuides. 



B. Pneumatic foramina of dorsal surface of sternum conspicuous, extending 

 along thb whole length of median line of the sternum ; carina merging 

 into the sternal plate some distance in front of the metasternum ; posterior 

 lateral processes projecting far beyond the level of the metasternum. 



Biomedeidce. 



D. Pelvic G-irdle. 



Pre- longer than post-acetabular ilium ; ischium produced far backwards in 

 the form of a long narrow bar of bone, its free end deflected and firmly bound 

 to, or even fused with, the pubis, so that the obturator fissure is closed 

 behind ; obturator foramen never completely shut ofl' from the fissure. 



A. Pre-ilia not meeting in the mid-dorsal line above the neural crest of the 

 synsacrum ; innominate free. 

 a. Size small, total length of pelvis not exceeding 1-4 in. ; postacetabular 

 ilium with its dorsal border obliquely truncated and ill-defined ; free 

 ends of ischium and pubis fused. 

 a'. Obturator fissure very narrow ; pre-ilia widely separated ; obturator 

 foramen open posteriorly ; lumbar enlargement of synsacrum large 

 and lying in front of the acetabular region. 



a". Pre-iliu- , not expanded distally Procellaria. 



b". Pre-iUum expanded distally Oceanodroma . 



b'. Obturator fissure very wide ; lumbar enlargement of synsacrum slight, 

 lying in mid-acetabular region, 

 c". Pre-ilia not rising beyond the level of the base of the synsacral 

 neural crest ; obim'ator foramen separated from the fissm'e by a 



broad bar of bone Pelagodroma. 



d". Pre-ilia rising to the level of the top of the neural crest, or 

 nearly so. 

 a^. Obturator foramen and fissure confluent. 



a<. Dorsal border of pre-ilium pressed closely to the lumbar en- 

 largement, which is almost entirely preacetabular ; greatest 



width of synsacrum about J its length Oceanites. 



b^. Dorsal border of pre-ilium separated by a deep groove from the 

 lumbar enlargement ; greatest width of synsacrum about \ its 



length Cymodroma, 



b^. Obturator foramen separated from the fissure by a broad bar of 

 bone; pre-ilia pointed in front .. Fregetta. 



27* 



